Wrong Answer
/in/foo.cc: In function 'void dfs(int)':
/in/foo.cc:9:10: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
if(n == s.length()){
~~^~~~~~~~~~~~~
/in/foo.cc:14:10: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
if(n < s.length()-1){
~~^~~~~~~~~~~~~~
